I'm building an animation where an object starts as wireframe, then transforms to solid. Blender 2.79b, Cycles.

I have two duplicates of the object, one of which has a wireframe modifier applied. Then I use an object (a cylinder for now) as a boolean object, set to Difference on the wireframe copy and Intersect on the solid copy. The boolean object has its Camera setting turned off in Cycles Settings. By animating the shape, position and scale of the boolean object, I can achieve what I'm looking for.

However, it would be cool to add a glow effect at the boundary, as if there's electric, transformative energy, say. I can't think of a way to do this. Any ideas?



1 Answer 1


More than one way.

Use a vertex weight proximity modifier after the boolean to assign vertices to a "glow" group, then use a UV warp modifier to translate this glow group into add UV that you can read in your shader.

enter image description here

Our boolean will create new vertices, and vertex weight proximity only affects vertices already assigned to the group, so we'll first need to use a vertex weight edit modifier, immediately following the boolean, to assign all verts to our glow group.

Then our vertex weight proximity modifier overrides that, assigning only vertices that are close to the cylinder (from 0 to 0.13 distance in this case.) We use that vertex group to warp a UV map where all verts have been mapped to 0,0 in order to convert weights to something readable by our nodes. The empties off to the side just establish a 1 unit X difference for the UV warp mod. See Weight paint in cycles nodes?.

I'm not sure how the boolean modifier generates UV coords. I believe it interpolates them from existing coords. Here, any verts created by the boolean are being written properly to our glow map at 0,0.

In our material, we're simply using our UV output from our glow map-- which, remember, represents the proximity of any face of the cylinder-- as strength. I'm doing a little math just to make it look better.

  • $\begingroup$ Thanks, Nathan! However, I'm finding I've got just too many holes in my knowledge of Blender to be able to recreate what you're proposing. Any chance you could share the blend file with me so I can pick it apart? $\endgroup$ Jun 27, 2018 at 20:01
  • $\begingroup$ pasteall.org/blend/index.php?id=49822 . I've done a little playing, might not be exactly what I describe, but should communicate the idea. $\endgroup$
    – Nathan
    Jun 27, 2018 at 20:14
  • $\begingroup$ Thanks! I got it working. I wish I could attach an image to a comment... The main thing I needed to play with was the position of one of my empties. Nothing made sense until I moved it further away, and then the glow started to look right. I also change the Add shader to a Mix shader, with the UV value going straight into the Factor, which worked great. $\endgroup$ Jun 27, 2018 at 22:27

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